Rose Rosette disease sweeps through Mercer County, gardeners forced to tear out plants

EWING — Dianne Dickinson has a special connection to the flower she’s been growing in her backyard for more than 30 years. She was born in the month of June, making the rose her “birth flower,” she said.

“I love them, and I’ve gotten really attached to them,” said Dickinson, who is president of the West Trenton Garden Club.

So Dickinson was concerned when she heard about more than a dozen cases of a disease called rose rosette that have been reported in Mercer County in the last two months, though she has not yet seen any symptoms on her own roses this season.

“They take a lot of time and effort to grow, so if you’re going to lose them, it’s awful,” she said. “I fear the possibility of losing such a beautiful flower.”

First detected in the western U.S. in the 1940s, the disease gradually began appearing on the East Coast over the last decade, plaguing local nurseries and home rose growers, said Barbara Bromley, horticulturist for the Rutgers Cooperative Extension of Mercer County. It is believed to be caused by a virus and affects all types of roses.

Spread by microscopic, wingless eriophyid mites that feed on the flower, rose rosette is extremely difficult to prevent, and the only way to treat an infected rosebush is to completely tear it out, roots and all, Bromley said. If untreated, the disease can slowly kill the flower in one to three years, she said.

The mites are so small that they are transmitted to healthy rosebushes by wind, and growers who tend an infected bush and then move on to a healthy one can unwittingly deliver the mites on their hands, Bromley said.

“It can spread in minutes, once the mites begin feeding on the plant,” she said.

She has even heard of the mites “hitchhiking” on other insects to feed on new flowers, she said.

“If your roses are diagnosed with rose rosette, you can try to get rid of the mites and prune it out, but in the long haul, it’s still in the plant,” she said. “The safest thing to do is to get rid of it.”

The mites’ primary host is Asian native multiflora rose that grows wild and is highly susceptible to the disease due to the millions of seeds it produces, Bromley said. The flower was brought to the U.S. more than 100 years ago to control wind and erosion along highways and for ornamental purposes, she said.

Bromley described the plant as “a royal pain in the neck.”

“Multiflora rose is everywhere and serves as a host for rose rosette, a huge disadvantage to landscape roses,” said Meredith Melendez, agriculture coordinator for the Rutgers Cooperative Extension of Mercer County, in an e-mail.

The disease has no known cure. Growers can try spraying pesticides on the mites to prevent them from feeding on their rosebushes, but the process is tedious because the mites are very tiny and growers would need to spray every mite in order for it to be effective, Bromley said.

“The lack of controls for rose rosette disease is frustrating for those with affected plants, and there are no known resistant varieties or roses available on the market,” Melendez said.

Symptoms are commonly mistaken for herbicide damage and include an overabundance of small thorns on the canes and vines of the flower, shriveled buds (if any), and clusters of distorted, burgundy-colored leaves that resemble a witch’s broom, Bromley said.

Terry Palise, a Lawrence resident and president of the West Jersey Rose Society, said she has been growing roses for nine years and has about 200 currently in her backyard. She saw rose rosette on her flowers for the first time about seven years ago and thinks the recent warm winters are helping to keep the mites alive, she said.

“We’re not really having really cold, snowy winters to kill them,” she said. “Thank goodness roses don’t cost as much as other things. I just kept planting more.”

Growers in the state are encouraged to check their roses routinely and contact experts at their county’s agriculture agency if they suspect the disease, Bromley said.

“Be alert for weird symptoms, and have it identified,” she said. “That’s what the extension is for, so we know too. If people didn’t bring me samples, we wouldn’t know it existed in our area.”

Samples can be dropped off for testing at her office at 930 Spruce St. in Trenton. Local growers with questions or concerns can call Bromley at (609) 989-6830.